SMAD7-mediated ferroptosis in macrophages drives osteoporosis progression: A multi-omics study

Osteoporosis (OP) is characterized by imbalanced bone homeostasis, which is difficult to precisely regulate with current therapeutic strategies. Macrophages play a significant role in bone remodeling due to their complex interactions with osteoclasts and osteoblasts, suggesting that targeting macrophage-related pathways could offer novel therapeutic opportunities. To explore this, we combined bulk RNA-seq and scRNA-seq data to identify macrophage-related genes. Using bioinformatic tools, including CIBERSORT, WGCNA, and machine learning algorithms, we identified 1705 macrophage marker genes and 839 macrophage module genes. Enrichment analysis revealed that the intersection genes were significantly enriched in the ferroptosis signaling pathway, highlighting its critical role in macrophages. Further validation through protein-protein interaction networks and cellular communication analysis confirmed the importance of ferroptosis in macrophage. Using artificial neural network, we identified 4 macrophage hub genes, with SMAD7 showing the greatest weight. Experimental validation using RAW264.7 cells, immunohistochemistry, and micro-CT analysis further demonstrated the association of ferroptosis-related indicators (Fe^{2 +} and lipid peroxidation) with bone damage in osteoporosis patients. And we found SMAD7 showing the strongest correlation with trabecular microstructural deterioration. Notably, our findings also confirmed that the SMAD7 inhibitor mongersen effectively attenuated macrophage ferroptosis, suggesting its potential to improve bone microstructural integrity. Our study demonstrates that SMAD7-mediated macrophage ferroptosis is a critical mechanism in osteoporosis pathogenesis, highlighting SMAD7 as a promising therapeutic target.